A064462 First row of Pascal's triangle that has n nonsquarefree entries, or -1 if no such row exists.

0, 6, 4, 14, 13, 10, 8, -1, 9, 12, -1, 22, 17, 20, -1, 16, -1, 18, 29, 26, 31, 24, 25, 62, -1, 28, 27, 34, 35, 42, 33, 32, -1, -1, -1, 36, 53, 40, 45, -1, -1, -1, 95, -1, -1, -1, 79, 48, 49, 50, 55, 54, 57, 60, 69, 56, 63, 74, -1, 70, 67, 66, 65, 64, 77, -1

Offset: 0

Author

Robert G. Wilson v, Oct 02 2001

Keywords

• sign

Comments

Numbers such that a(n) is -1: 7, 10, 14, 16, 24, 32, 33, 34, 39, 40, 41, 43, ... - Michel Marcus, Mar 05 2014

Examples

			a(4) = 13 because C(13,5) = C(13,8) = 3^2*11*13 and C(13,6) = C(13,7) = 2^2*3*11*13.
		

Crossrefs

Cf. A048277, A064461.

Programs

Mathematica

f[ n_ ] := (c = 0; k = 1; While[ k < n, If[ Union[ Transpose[ FactorInteger[ Binomial[ n, k ] ] ] [ [ 2 ] ] ] [ [ -1 ] ] > 1, c++ ]; k++ ]; c); Do[ m = 2; While[ f[ m ] != n, m++ ]; Print[ m ], {n, 0, 6} ]

PARI

a(n, v) = {for (i=1, #v, if (v[i] == n, return (i-1));); return (-1);} \\ where v is vector A048277; Michel Marcus, Mar 05 2014

Extensions

Corrected and extended by Michel Marcus, Mar 05 2014